At present, sorbitol diacetal is generally used as a basic ingredient of a sorbitol nucleator used industrially. Sorbitol acetal and sorbitol triacetal are needed to be removed from the sorbitol nucleator as impurities. Alternatively, the reaction condition of a preparation process of sorbitol diacetal needs to be controlled, so as to avoid generating sorbitol acetal and triacetal. For instance, Chinese patent application, CN 200410026622.8, discloses a method for purifying nucleators, in which methylene benzylidene sorbitol and trimethylene benzylidene sorbitol are removed to improve the purity of the nucleator. However, in CN 200410026622.8, the purity of the purified nucleator cannot reach 100% yet, and the impurities and concentrations thereof in the nucleator cannot be determined.
Other sorbitol nucleators may contain too much triacetal or contain no triacetal. For instance, Chinese patent application CN 200810219978.1 discloses a method for preparing nucleators. During the preparation of the nucleator, the amount of aromatic aldehyde added, the reaction time and reaction temperature are controlled. Because no special attention has been paid to the order of addition, triacetal and diacetal in the products cannot be controlled precisely. Moreover, effects of particular concentrations of triacetal in the nucleator on the performances of the products have not been studied.